How a vehicle occupant’s body moves during a collision varies greatly based on their posture at the time of impact—was it unexpected and they were relaxed, or did they see it coming and brace for the inevitable? And when designing a vehicle’s safety systems, like seatbelts, crumple zones, and air bags, every possible outcome needs to be taken into consideration.

Current virtual crash simulator technology isn’t able to take into an account a passenger who’s braced themselves for impact—like pressing their feet against the vehicle’s floorboards. So Toyota has added an upgraded muscle structure to the latest version of its virtual passengers model which it calls the Total Human Model for Safety—or THUMS, for short.

The improved virtual crash test dummies (which no longer sound that dumb) can now test new vehicle and safety equipment designs using a host of new scenarios where passengers aren’t just sitting relaxed in their seats, oblivious to what’s about to happen. The upgraded THUMS models are now also able to better predict broken bones, crushed organs, and other serious injuries.

Decades ago there was a good chance that most passengers involved in an accident didn’t see it coming and didn’t have time to take defensive actions, like swerving or braking, ahead of the impact. But as many modern vehicles now include sensors and advanced warning safety features, the odds of a passenger having a split-second to react are improved, and carmakers need to be able to account for this in their designs.